/*
** $Id: loadlib.c $
** Dynamic library loader for Lua
** See Copyright Notice in lua.h
**
** This module contains an implementation of loadlib for Unix systems
** that have dlfcn, an implementation for Windows, and a stub for other
** systems.
*/

#define loadlib_c
#define LUA_LIB

#include "lprefix.h"


#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "lua.h"

#include "lauxlib.h"
#include "lualib.h"

#include "lua_module.h"
/*
** LUA_IGMARK is a mark to ignore all before it when building the
** luaopen_ function name.
*/
#if !defined (LUA_IGMARK)
#define LUA_IGMARK      "-"
#endif


/*
** LUA_CSUBSEP is the character that replaces dots in submodule names
** when searching for a C loader.
** LUA_LSUBSEP is the character that replaces dots in submodule names
** when searching for a Lua loader.
*/
#if !defined(LUA_CSUBSEP)
#define LUA_CSUBSEP     LUA_DIRSEP
#endif

#if !defined(LUA_LSUBSEP)
#define LUA_LSUBSEP     LUA_DIRSEP
#endif


/* prefix for open functions in C libraries */
#define LUA_POF     "luaopen_"

/* separator for open functions in C libraries */
#define LUA_OFSEP   "_"


/*
** key for table in the registry that keeps handles
** for all loaded C libraries
*/
static const char* const CLIBS = "_CLIBS";

#define LIB_FAIL    "open"


#define setprogdir(L)           ((void)0)


/*
** Special type equivalent to '(void*)' for functions in gcc
** (to suppress warnings when converting function pointers)
*/
typedef void (*voidf)(void);


/*
** system-dependent functions
*/

/*
** unload library 'lib'
*/
static void lsys_unloadlib (void* lib);

/*
** load C library in file 'path'. If 'seeglb', load with all names in
** the library global.
** Returns the library; in case of error, returns NULL plus an
** error string in the stack.
*/
static void* lsys_load (lua_State* L, const char* path, int seeglb);

/*
** Try to find a function named 'sym' in library 'lib'.
** Returns the function; in case of error, returns NULL plus an
** error string in the stack.
*/
static lua_CFunction lsys_sym (lua_State* L, void* lib, const char* sym);




#if defined(LUA_USE_DLOPEN) /* { */
/*
** {========================================================================
** This is an implementation of loadlib based on the dlfcn interface.
** The dlfcn interface is available in Linux, SunOS, Solaris, IRIX, FreeBSD,
** NetBSD, AIX 4.2, HPUX 11, and  probably most other Unix flavors, at least
** as an emulation layer on top of native functions.
** =========================================================================
*/

#include <dlfcn.h>

/*
** Macro to convert pointer-to-void* to pointer-to-function. This cast
** is undefined according to ISO C, but POSIX assumes that it works.
** (The '__extension__' in gnu compilers is only to avoid warnings.)
*/
#if defined(__GNUC__)
#define cast_func(p) (__extension__ (lua_CFunction)(p))
#else
#define cast_func(p) ((lua_CFunction)(p))
#endif


static void lsys_unloadlib (void* lib)
{
    dlclose(lib);
}


static void* lsys_load (lua_State* L, const char* path, int seeglb)
{
    void* lib = dlopen(path, RTLD_NOW | (seeglb ? RTLD_GLOBAL : RTLD_LOCAL));

    if (l_unlikely(lib == NULL))
    {
        lua_pushstring(L, dlerror());
    }

    return lib;
}


static lua_CFunction lsys_sym (lua_State* L, void* lib, const char* sym)
{
    lua_CFunction f = cast_func(dlsym(lib, sym));

    if (l_unlikely(f == NULL))
    {
        lua_pushstring(L, dlerror());
    }

    return f;
}

/* }====================================================== */



#elif defined(LUA_DL_DLL)   /* }{ */
/*
** {======================================================================
** This is an implementation of loadlib for Windows using native functions.
** =======================================================================
*/

#include <windows.h>


/*
** optional flags for LoadLibraryEx
*/
#if !defined(LUA_LLE_FLAGS)
#define LUA_LLE_FLAGS   0
#endif


#undef setprogdir


/*
** Replace in the path (on the top of the stack) any occurrence
** of LUA_EXEC_DIR with the executable's path.
*/
static void setprogdir (lua_State* L)
{
    char buff[MAX_PATH + 1];
    char* lb;
    DWORD nsize = sizeof(buff)/sizeof(char);
    DWORD n = GetModuleFileNameA(NULL, buff, nsize);  /* get exec. name */

    if (n == 0 || n == nsize || (lb = strrchr(buff, '\\')) == NULL)
    {
        luaL_error(L, "unable to get ModuleFileName");
    }
    else
    {
        *lb = '\0';  /* cut name on the last '\\' to get the path */
        luaL_gsub(L, lua_tostring(L, -1), LUA_EXEC_DIR, buff);
        lua_remove(L, -2);  /* remove original string */
    }
}




static void pusherror (lua_State* L)
{
    int error = GetLastError();
    char buffer[128];

    if (FormatMessageA(FORMAT_MESSAGE_IGNORE_INSERTS | FORMAT_MESSAGE_FROM_SYSTEM,
                       NULL, error, 0, buffer, sizeof(buffer)/sizeof(char), NULL))
    {
        lua_pushstring(L, buffer);
    }
    else
    {
        lua_pushfstring(L, "system error %d\n", error);
    }
}

static void lsys_unloadlib (void* lib)
{
    FreeLibrary((HMODULE)lib);
}


static void* lsys_load (lua_State* L, const char* path, int seeglb)
{
    HMODULE lib = LoadLibraryExA(path, NULL, LUA_LLE_FLAGS);
    (void)(seeglb);  /* not used: symbols are 'global' by default */

    if (lib == NULL)
    {
        pusherror(L);
    }

    return lib;
}


static lua_CFunction lsys_sym (lua_State* L, void* lib, const char* sym)
{
    lua_CFunction f = (lua_CFunction)(voidf)GetProcAddress((HMODULE)lib, sym);

    if (f == NULL)
    {
        pusherror(L);
    }

    return f;
}

/* }====================================================== */


#else               /* }{ */
/*
** {======================================================
** Fallback for other systems
** =======================================================
*/

#undef LIB_FAIL
#define LIB_FAIL    "absent"


#define DLMSG   "dynamic libraries not enabled; check your Lua installation"


static void lsys_unloadlib (void* lib)
{
    (void)(lib);  /* not used */
}


static void* lsys_load (lua_State* L, const char* path, int seeglb)
{
    (void)(path);
    (void)(seeglb);  /* not used */
    lua_pushliteral(L, DLMSG);
    return NULL;
}


static lua_CFunction lsys_sym (lua_State* L, void* lib, const char* sym)
{
    (void)(lib);
    (void)(sym);  /* not used */
    lua_pushliteral(L, DLMSG);
    return NULL;
}

/* }====================================================== */
#endif              /* } */


/*
** {==================================================================
** Set Paths
** ===================================================================
*/

/*
** LUA_PATH_VAR and LUA_CPATH_VAR are the names of the environment
** variables that Lua check to set its paths.
*/
#if !defined(LUA_PATH_VAR)
#define LUA_PATH_VAR    "LUA_PATH"
#endif

#if !defined(LUA_CPATH_VAR)
#define LUA_CPATH_VAR   "LUA_CPATH"
#endif



/*
** return registry.LUA_NOENV as a boolean
*/
static int noenv (lua_State* L)
{
    int b;
    lua_getfield(L, LUA_REGISTRYINDEX, "LUA_NOENV");
    b = lua_toboolean(L, -1);
    lua_pop(L, 1);  /* remove value */
    return b;
}


/*
** Set a path
*/
static void setpath (lua_State* L, const char* fieldname,
                     const char* envname,
                     const char* dft)
{
    const char* dftmark;
    const char* nver = lua_pushfstring(L, "%s%s", envname, LUA_VERSUFFIX);
    const char* path = getenv(nver);  /* try versioned name */

    if (path == NULL)  /* no versioned environment variable? */
    {
        path = getenv(envname);    /* try unversioned name */
    }

    if (path == NULL || noenv(L))  /* no environment variable? */
    {
        lua_pushstring(L, dft);    /* use default */
    }
    else if ((dftmark = strstr(path, LUA_PATH_SEP LUA_PATH_SEP)) == NULL)
    {
        lua_pushstring(L, path);    /* nothing to change */
    }
    else    /* path contains a ";;": insert default path in its place */
    {
        size_t len = strlen(path);
        luaL_Buffer b;
        luaL_buffinit(L, &b);

        if (path < dftmark)    /* is there a prefix before ';;'? */
        {
            luaL_addlstring(&b, path, dftmark - path);  /* add it */
            luaL_addchar(&b, *LUA_PATH_SEP);
        }

        luaL_addstring(&b, dft);  /* add default */

        if (dftmark < path + len - 2)    /* is there a suffix after ';;'? */
        {
            luaL_addchar(&b, *LUA_PATH_SEP);
            luaL_addlstring(&b, dftmark + 2, (path + len - 2) - dftmark);
        }

        luaL_pushresult(&b);
    }

    setprogdir(L);
    lua_setfield(L, -3, fieldname);  /* package[fieldname] = path value */
    lua_pop(L, 1);  /* pop versioned variable name ('nver') */
}

/* }================================================================== */


/*
** return registry.CLIBS[path]
*/
static void* checkclib (lua_State* L, const char* path)
{
    void* plib;
    lua_getfield(L, LUA_REGISTRYINDEX, CLIBS);
    lua_getfield(L, -1, path);
    plib = lua_touserdata(L, -1);  /* plib = CLIBS[path] */
    lua_pop(L, 2);  /* pop CLIBS table and 'plib' */
    return plib;
}


/*
** registry.CLIBS[path] = plib        -- for queries
** registry.CLIBS[#CLIBS + 1] = plib  -- also keep a list of all libraries
*/
static void addtoclib (lua_State* L, const char* path, void* plib)
{
    lua_getfield(L, LUA_REGISTRYINDEX, CLIBS);
    lua_pushlightuserdata(L, plib);
    lua_pushvalue(L, -1);
    lua_setfield(L, -3, path);  /* CLIBS[path] = plib */
    lua_rawseti(L, -2, luaL_len(L, -2) + 1);  /* CLIBS[#CLIBS + 1] = plib */
    lua_pop(L, 1);  /* pop CLIBS table */
}


/*
** __gc tag method for CLIBS table: calls 'lsys_unloadlib' for all lib
** handles in list CLIBS
*/
static int gctm (lua_State* L)
{
    lua_Integer n = luaL_len(L, 1);

    for (; n >= 1; n--)    /* for each handle, in reverse order */
    {
        lua_rawgeti(L, 1, n);  /* get handle CLIBS[n] */
        lsys_unloadlib(lua_touserdata(L, -1));
        lua_pop(L, 1);  /* pop handle */
    }

    return 0;
}



/* error codes for 'lookforfunc' */
#define ERRLIB      1
#define ERRFUNC     2

/*
** Look for a C function named 'sym' in a dynamically loaded library
** 'path'.
** First, check whether the library is already loaded; if not, try
** to load it.
** Then, if 'sym' is '*', return true (as library has been loaded).
** Otherwise, look for symbol 'sym' in the library and push a
** C function with that symbol.
** Return 0 and 'true' or a function in the stack; in case of
** errors, return an error code and an error message in the stack.
*/
static int lookforfunc (lua_State* L, const char* path, const char* sym)
{
    void* reg = checkclib(L, path);  /* check loaded C libraries */

    if (reg == NULL)    /* must load library? */
    {
        reg = lsys_load(L, path, *sym == '*');  /* global symbols if 'sym'=='*' */

        if (reg == NULL)
        {
            return ERRLIB;    /* unable to load library */
        }

        addtoclib(L, path, reg);
    }

    if (*sym == '*')    /* loading only library (no function)? */
    {
        lua_pushboolean(L, 1);  /* return 'true' */
        return 0;  /* no errors */
    }
    else
    {
        lua_CFunction f = lsys_sym(L, reg, sym);

        if (f == NULL)
        {
            return ERRFUNC;    /* unable to find function */
        }

        lua_pushcfunction(L, f);  /* else create new function */
        return 0;  /* no errors */
    }
}


static int ll_loadlib (lua_State* L)
{
    const char* path = luaL_checkstring(L, 1);
    const char* init = luaL_checkstring(L, 2);
    int stat = lookforfunc(L, path, init);

    if (l_likely(stat == 0))  /* no errors? */
    {
        return 1;    /* return the loaded function */
    }
    else    /* error; error message is on stack top */
    {
        luaL_pushfail(L);
        lua_insert(L, -2);
        lua_pushstring(L, (stat == ERRLIB) ?  LIB_FAIL : "init");
        return 3;  /* return fail, error message, and where */
    }
}



/*
** {======================================================
** 'require' function
** =======================================================
*/


static int readable (const char* filename)
{
    FILE* f = fopen(filename, "r");  /* try to open file */

    if (f == NULL)
    {
        return 0;    /* open failed */
    }

    fclose(f);
    return 1;
}


/*
** Get the next name in '*path' = 'name1;name2;name3;...', changing
** the ending ';' to '\0' to create a zero-terminated string. Return
** NULL when list ends.
*/
static const char* getnextfilename (char** path, char* end)
{
    char* sep;
    char* name = *path;

    if (name == end)
    {
        return NULL;    /* no more names */
    }
    else if (*name == '\0')    /* from previous iteration? */
    {
        *name = *LUA_PATH_SEP;  /* restore separator */
        name++;  /* skip it */
    }

    sep = strchr(name, *LUA_PATH_SEP);  /* find next separator */

    if (sep == NULL)  /* separator not found? */
    {
        sep = end;    /* name goes until the end */
    }

    *sep = '\0';  /* finish file name */
    *path = sep;  /* will start next search from here */
    return name;
}


/*
** Given a path such as ";blabla.so;blublu.so", pushes the string
**
** no file 'blabla.so'
**  no file 'blublu.so'
*/
static void pusherrornotfound (lua_State* L, const char* path)
{
    luaL_Buffer b;
    luaL_buffinit(L, &b);
    luaL_addstring(&b, "no file '");
    luaL_addgsub(&b, path, LUA_PATH_SEP, "'\n\tno file '");
    luaL_addstring(&b, "'");
    luaL_pushresult(&b);
}


static const char* searchpath (lua_State* L, const char* name,
                               const char* path,
                               const char* sep,
                               const char* dirsep)
{
    luaL_Buffer buff;
    char* pathname;  /* path with name inserted */
    char* endpathname;  /* its end */
    const char* filename;

    /* separator is non-empty and appears in 'name'? */
    if (*sep != '\0' && strchr(name, *sep) != NULL)
    {
        name = luaL_gsub(L, name, sep, dirsep);    /* replace it by 'dirsep' */
    }

    luaL_buffinit(L, &buff);
    /* add path to the buffer, replacing marks ('?') with the file name */
    luaL_addgsub(&buff, path, LUA_PATH_MARK, name);
    luaL_addchar(&buff, '\0');
    pathname = luaL_buffaddr(&buff);  /* writable list of file names */
    endpathname = pathname + luaL_bufflen(&buff) - 1;

    while ((filename = getnextfilename(&pathname, endpathname)) != NULL)
    {
        if (readable(filename))  /* does file exist and is readable? */
        {
            return lua_pushstring(L, filename);    /* save and return name */
        }
    }

    luaL_pushresult(&buff);  /* push path to create error message */
    pusherrornotfound(L, lua_tostring(L, -1));  /* create error message */
    return NULL;  /* not found */
}


static int ll_searchpath (lua_State* L)
{
    const char* f = searchpath(L, luaL_checkstring(L, 1),
                               luaL_checkstring(L, 2),
                               luaL_optstring(L, 3, "."),
                               luaL_optstring(L, 4, LUA_DIRSEP));

    if (f != NULL)
    {
        return 1;
    }
    else    /* error message is on top of the stack */
    {
        luaL_pushfail(L);
        lua_insert(L, -2);
        return 2;  /* return fail + error message */
    }
}


static const char* findfile (lua_State* L, const char* name,
                             const char* pname,
                             const char* dirsep)
{
    const char* path;
    lua_getfield(L, lua_upvalueindex(1), pname);
    path = lua_tostring(L, -1);

    if (l_unlikely(path == NULL))
    {
        luaL_error(L, "'package.%s' must be a string", pname);
    }

    return searchpath(L, name, path, ".", dirsep);
}


static int checkload (lua_State* L, int stat, const char* filename)
{
    if (l_likely(stat))    /* module loaded successfully? */
    {
        lua_pushstring(L, filename);  /* will be 2nd argument to module */
        return 2;  /* return open function and file name */
    }
    else
        return luaL_error(L, "error loading module '%s' from file '%s':\n\t%s",
                          lua_tostring(L, 1), filename, lua_tostring(L, -1));
}


static int searcher_Lua (lua_State* L)
{
    const char* filename;
    const char* name = luaL_checkstring(L, 1);
    filename = findfile(L, name, "path", LUA_LSUBSEP);

    if (filename == NULL)
    {
        return 1;    /* module not found in this path */
    }

    return checkload(L, (luaL_loadfile(L, filename) == LUA_OK), filename);
}


/*
** Try to find a load function for module 'modname' at file 'filename'.
** First, change '.' to '_' in 'modname'; then, if 'modname' has
** the form X-Y (that is, it has an "ignore mark"), build a function
** name "luaopen_X" and look for it. (For compatibility, if that
** fails, it also tries "luaopen_Y".) If there is no ignore mark,
** look for a function named "luaopen_modname".
*/
static int loadfunc (lua_State* L, const char* filename, const char* modname)
{
    const char* openfunc;
    const char* mark;
    modname = luaL_gsub(L, modname, ".", LUA_OFSEP);
    mark = strchr(modname, *LUA_IGMARK);

    if (mark)
    {
        int stat;
        openfunc = lua_pushlstring(L, modname, mark - modname);
        openfunc = lua_pushfstring(L, LUA_POF"%s", openfunc);
        stat = lookforfunc(L, filename, openfunc);

        if (stat != ERRFUNC)
        {
            return stat;
        }

        modname = mark + 1;  /* else go ahead and try old-style name */
    }

    openfunc = lua_pushfstring(L, LUA_POF"%s", modname);
    return lookforfunc(L, filename, openfunc);
}


static int searcher_C (lua_State* L)
{
    const char* name = luaL_checkstring(L, 1);
    const char* filename = findfile(L, name, "cpath", LUA_CSUBSEP);

    if (filename == NULL)
    {
        return 1;    /* module not found in this path */
    }

    return checkload(L, (loadfunc(L, filename, name) == 0), filename);
}


static int searcher_Croot (lua_State* L)
{
    const char* filename;
    const char* name = luaL_checkstring(L, 1);
    const char* p = strchr(name, '.');
    int stat;

    if (p == NULL)
    {
        return 0;    /* is root */
    }

    lua_pushlstring(L, name, p - name);
    filename = findfile(L, lua_tostring(L, -1), "cpath", LUA_CSUBSEP);

    if (filename == NULL)
    {
        return 1;    /* root not found */
    }

    if ((stat = loadfunc(L, filename, name)) != 0)
    {
        if (stat != ERRFUNC)
        {
            return checkload(L, 0, filename);    /* real error */
        }
        else    /* open function not found */
        {
            lua_pushfstring(L, "no module '%s' in file '%s'", name, filename);
            return 1;
        }
    }

    lua_pushstring(L, filename);  /* will be 2nd argument to module */
    return 2;
}


static int searcher_preload (lua_State* L)
{
    const char* name = luaL_checkstring(L, 1);
    lua_getfield(L, LUA_REGISTRYINDEX, LUA_PRELOAD_TABLE);

    if (lua_getfield(L, -1, name) == LUA_TNIL)    /* not found? */
    {
        lua_pushfstring(L, "no field package.preload['%s']", name);
        return 1;
    }
    else
    {
        lua_pushliteral(L, ":preload:");
        return 2;
    }
}


static void findloader (lua_State* L, const char* name)
{
    int i;
    luaL_Buffer msg;  /* to build error message */

    /* push 'package.searchers' to index 3 in the stack */
    if (l_unlikely(lua_getfield(L, lua_upvalueindex(1), "searchers")
                   != LUA_TTABLE))
    {
        luaL_error(L, "'package.searchers' must be a table");
    }

    luaL_buffinit(L, &msg);

    /*  iterate over available searchers to find a loader */
    for (i = 1; ; i++)
    {
        luaL_addstring(&msg, "\n\t");  /* error-message prefix */

        if (l_unlikely(lua_rawgeti(L, 3, i) == LUA_TNIL))    /* no more searchers? */
        {
            lua_pop(L, 1);  /* remove nil */
            luaL_buffsub(&msg, 2);  /* remove prefix */
            luaL_pushresult(&msg);  /* create error message */
            luaL_error(L, "module '%s' not found:%s", name, lua_tostring(L, -1));
        }

        lua_pushstring(L, name);
        lua_call(L, 1, 2);  /* call it */

        if (lua_isfunction(L, -2))  /* did it find a loader? */
        {
            return;    /* module loader found */
        }
        else if (lua_isstring(L, -2))    /* searcher returned error message? */
        {
            lua_pop(L, 1);  /* remove extra return */
            luaL_addvalue(&msg);  /* concatenate error message */
        }
        else    /* no error message */
        {
            lua_pop(L, 2);  /* remove both returns */
            luaL_buffsub(&msg, 2);  /* remove prefix */
        }
    }
}


static int ll_require (lua_State* L)
{
    const char* name = luaL_checkstring(L, 1);
    lua_settop(L, 1);  /* LOADED table will be at index 2 */
    lua_getfield(L, LUA_REGISTRYINDEX, LUA_LOADED_TABLE);
    lua_getfield(L, 2, name);  /* LOADED[name] */

    if (lua_toboolean(L, -1))  /* is it there? */
    {
        return 1;    /* package is already loaded */
    }

    /* else must load package */
    lua_pop(L, 1);  /* remove 'getfield' result */
    findloader(L, name);
    lua_rotate(L, -2, 1);  /* function <-> loader data */
    lua_pushvalue(L, 1);  /* name is 1st argument to module loader */
    lua_pushvalue(L, -3);  /* loader data is 2nd argument */
    /* stack: ...; loader data; loader function; mod. name; loader data */
    lua_call(L, 2, 1);  /* run loader to load module */

    /* stack: ...; loader data; result from loader */
    if (!lua_isnil(L, -1))  /* non-nil return? */
    {
        lua_setfield(L, 2, name);    /* LOADED[name] = returned value */
    }
    else
    {
        lua_pop(L, 1);    /* pop nil */
    }

    if (lua_getfield(L, 2, name) == LUA_TNIL)     /* module set no value? */
    {
        lua_pushboolean(L, 1);  /* use true as result */
        lua_copy(L, -1, -2);  /* replace loader result */
        lua_setfield(L, 2, name);  /* LOADED[name] = true */
    }

    lua_rotate(L, -2, 1);  /* loader data <-> module result  */
    return 2;  /* return module result and loader data */
}

/*
** {======================================================
** 'module' function
** =======================================================
*/
#if defined(LUA_COMPAT_MODULE)

/*
** changes the environment variable of calling function
*/
static void set_env( lua_State* L )
{
    lua_Debug ar;

    if ( lua_getstack( L, 1, &ar ) == 0 ||
            lua_getinfo( L, "f", &ar ) == 0 || /* get calling function */
            lua_iscfunction( L, -1 ) )
    {
        luaL_error( L, "'module' not called from a Lua function" );
    }

    lua_pushvalue( L, -2 ); /* copy new environment table to top */
    lua_setupvalue( L, -2, 1 );
    lua_pop( L, 1 ); /* remove function */
}


static void dooptions( lua_State* L, int n )
{
    int i;

    for ( i = 2; i <= n; i++ )
    {
        if ( lua_isfunction( L, i ) )   /* avoid 'calling' extra info. */
        {
            lua_pushvalue( L, i ); /* get option (a function) */
            lua_pushvalue( L, -2 ); /* module */
            lua_call( L, 1, 0 );
        }
    }
}


static void modinit( lua_State* L, const char* modname )
{
    const char* dot;
    lua_pushvalue( L, -1 );
    lua_setfield( L, -2, "_M" ); /* module._M = module */
    lua_pushstring( L, modname );
    lua_setfield( L, -2, "_NAME" );
    dot = strrchr( modname, '.' ); /* look for last dot in module name */

    if ( dot == NULL )
    {
        dot = modname;
    }
    else
    {
        dot++;
    }

    /* set _PACKAGE as package name (full module name minus last part) */
    lua_pushlstring( L, modname, dot - modname );
    lua_setfield( L, -2, "_PACKAGE" );
}


static int ll_module( lua_State* L )
{
    const char* modname = luaL_checkstring( L, 1 );
    int lastarg = lua_gettop( L ); /* last parameter */
    luaL_pushmodule( L, modname, 1 ); /* get/create module table */

    /* check whether table already has a _NAME field */
    if ( lua_getfield( L, -1, "_NAME" ) != LUA_TNIL )
    {
        lua_pop( L, 1 );    /* table is an initialized module */
    }
    else    /* no; initialize it */
    {
        lua_pop( L, 1 );
        modinit( L, modname );
    }

    lua_pushvalue( L, -1 );
    set_env( L );
    dooptions( L, lastarg );
    return 1;
}


static int ll_seeall( lua_State* L )
{
    luaL_checktype( L, 1, LUA_TTABLE );

    if ( !lua_getmetatable( L, 1 ) )
    {
        lua_createtable( L, 0, 1 ); /* create new metatable */
        lua_pushvalue( L, -1 );
        lua_setmetatable( L, 1 );
    }

    lua_pushglobaltable( L );
    lua_setfield( L, -2, "__index" ); /* mt.__index = _G */
    return 0;
}

#endif

/* }====================================================== */

static const luaL_Reg pk_funcs[] =
{
    {"loadlib", ll_loadlib},
    {"searchpath", ll_searchpath},
#if defined(LUA_COMPAT_MODULE)
    {"seeall", ll_seeall},
#endif
    /* placeholders */
    {"preload", NULL},
    {"cpath", NULL},
    {"path", NULL},
    {"searchers", NULL},
    {"loaded", NULL},
    {NULL, NULL}
};


static const luaL_Reg ll_funcs[] =
{
#if defined(LUA_COMPAT_MODULE)
    {"module", ll_module},
#endif
    {"require", ll_require},
    {NULL, NULL}
};


static void createsearcherstable (lua_State* L)
{
    static const lua_CFunction searchers[] =
    {searcher_preload, searcher_Lua, searcher_C, searcher_Croot, NULL};
    int i;
    /* create 'searchers' table */
    lua_createtable(L, sizeof(searchers)/sizeof(searchers[0]) - 1, 0);

    /* fill it with predefined searchers */
    for (i=0; searchers[i] != NULL; i++)
    {
        lua_pushvalue(L, -2);  /* set 'package' as upvalue for all searchers */
        lua_pushcclosure(L, searchers[i], 1);
        lua_rawseti(L, -2, i+1);
    }

    lua_setfield(L, -2, "searchers");  /* put it in field 'searchers' */
}


/*
** create table CLIBS to keep track of loaded C libraries,
** setting a finalizer to close all libraries when closing state.
*/
static void createclibstable (lua_State* L)
{
    luaL_getsubtable(L, LUA_REGISTRYINDEX, CLIBS);  /* create CLIBS table */
    lua_createtable(L, 0, 1);  /* create metatable for CLIBS */
    lua_pushcfunction(L, gctm);
    lua_setfield(L, -2, "__gc");  /* set finalizer for CLIBS table */
    lua_setmetatable(L, -2);
}


LUAMOD_API int luaopen_package (lua_State* L)
{
    createclibstable(L);
    luaL_newlib(L, pk_funcs);  /* create 'package' table */
    createsearcherstable(L);
    /* set paths */
    setpath(L, "path", LUA_PATH_VAR, LUA_PATH_DEFAULT);
    setpath(L, "cpath", LUA_CPATH_VAR, LUA_CPATH_DEFAULT);
    /* store config information */
    lua_pushliteral(L, LUA_DIRSEP "\n" LUA_PATH_SEP "\n" LUA_PATH_MARK "\n"
                    LUA_EXEC_DIR "\n" LUA_IGMARK "\n");
    lua_setfield(L, -2, "config");
    /* set field 'loaded' */
    luaL_getsubtable(L, LUA_REGISTRYINDEX, LUA_LOADED_TABLE);
    lua_setfield(L, -2, "loaded");
    /* set field 'preload' */
    luaL_getsubtable(L, LUA_REGISTRYINDEX, LUA_PRELOAD_TABLE);
    lua_setfield(L, -2, "preload");
    lua_pushglobaltable(L);
    lua_pushvalue(L, -2);  /* set 'package' as upvalue for next lib */
    luaL_setfuncs(L, ll_funcs, 1);  /* open lib into global table */
    lua_pop(L, 1);  /* pop global table */
    return 1;  /* return 'package' table */
}

